This may sound silly, but I do not know the wavelength of the IR LEDs I’m using. The store I purchased them from are kinda hopeless, and even asking the voltage seemed to create a challenge. I could guess, but was wondering if there is a effective way of determining this.

I was thinking along the lines of incrementally layers floppy disk material over the camera, and perhaps the IR light will appear brighter with various layering setups. But I may be wrong (probably)

If you can, try get access to an few different IR bandpass filters of various wavelengths such as 780 830 850 etc and keep trying them untill you get light. I’m not sure who could do that where you are. Maybe a specialist shop that deals with IR equipment

Yeah, sounds like a plan. Was thinking that I should perhaps visit a company that sell security cameras, as those normally have Night Vision modes that use IR light. Perhaps they have some testing equipment. Thank you!

@Misz! Thank you very much. If I can get this to work, I’ll be super stoked.

However, after having read that Wiki, I realise that it’s highly unlikely that I could replicate an experiment like this without special equipment. I do like that it exposes just a little bit of the physics we are using to make our MTs work. I’ve kinda taken that for granted up until now…

Well what you need is a double slit. Which is a black piece of glass with two slits in it.

I have been using the technique with lasers, which have focused light, so I guess when using a LED you might need something to filter out the light from the LED that does not pass through the double slit. I recommend something black to absorb the light instead of reflecting it.

And this page better describes how to put the experiment together. (Youngs Experiment)

Neat test…

You can actually do the single slit experiment wherever you are right now! Hold two of your fingers very close together; there should be only the tiniest little gap between them that you can barely see through. Look towards a light source, light a light bulb, through the gap in your fingers. In the gap between your fingers you shold see very faint gray lines that run parallel to your fingers… these are the destructive interference “dark” fringes!

You need a simple way, which is not precise but easy to apply.
1. power on your led.
2. observe
(1) if you or someone of your friends(depends) could observe a tight red ------ <850nm
(2)nothing, but red via your phone-carried-camera ------ 940nm
(3) nothing red, even with every cameras you could found ------ 1030nm or farther

Hey,
You can even measure the wavelength with a single slit, it gives you a similar interference pattern as in the double slit experiment. But I think, its easier create a single slit, with a measurable width, than two of them. It also gives you the better results, because in the double slit experiment you basicaly have two single slit interference patterns, that interfere again.

This experiment works quite well, if you can do it under good conditions. Do it in total darkness, and observe the interfernce pattern with a camera that senses IR. Try to make the slit as small as possible, the smaller the slit is, the better you can see the interference pattern. If the slit is too large, there will only be light bending on the edges. Unfortuantely a small slit reduces light intensity.

Try to choose the distance between slit and the projection surface as long as possible.